This proposal describes a case-control study of the epidemiology of prolapsed lumbar intervertebral disc and prolapsed cervical intervertebral disc, conditions frequently seen in general practice as well as in the specialized practices of neurosurgery and othopaedic surgery. Demographic characteristics and exposure to possible risk factors in surgical, probable, and possible cases of each of these conditions in the age range 20-64 years will be compared to demographic characteristics and exposure to possible risk factors in two control groups in the same age range. One control group will be composed of people without known spinal disorders and the second will comprise people with back and neck problems other than prolapsed discs. Persons with previous prolapsed discs or other previous significant back or neck problems will be excluded from the case and control groups. Information on demographic variables and exposure to risk factors will be obtained by means of a structured questionnaire administered by trained interviewers. The questionnaire will cover symptoms of current and previous back, neck, leg, and arm problems; respiratory symptoms; demographic varibles; pregnancy history; occupational history; driving motor vehicles on job; driving other than on job; use of other modes of transportation; participation in certain sports; handedness; height, weight, and leg length; and disability and limitation of activity.